How confident are you that you will be able to recharge the batteries and continue the mission? And how long will it be until that is achieved? Congrats by the way on the landing! It's such a bummer to see something like batteries doom the project. I thought that was just a simpleton problem!

Well, it isn't really the batteries' fault! The batteries were meant to be recharged by solar panels but because Philae hopped a couple of times after the first touchdown, it ended up in shadow for nearly all the time (roughly one hour of sunlight every 12-hour "day" on the comet). It is like trying to power your house with solar panels when you live in Alaska just below the arctic circle during the winter. We are not sure yet where Philae is, but if it is at what some people think is the most likely place, the seasonal change toward spring in Philae's hemisphere should bring Philae into much more sunlight on a time scale of months. That, coupled with the fact that the comet is getting closer to the sun, should warm up the batteries enough to take a charge and then keep them charged. I.e, don't blame the batteries, blame Philae for wanting to go into a winter den for hibernation. ma

We expect to have enough energy to boot around March next year.
Then Philae needs to be heated until we can think of starting to charge the battery. So enough power to run the system, heat it and do charging or other operations we can expect early summer. Once charging can be started, it might take some comet days to charge the battery completely. [mm]

We will probably disagree on which discovery was most significant. For me the most significant discovery from the Rosetta orbiter thus far is that the outgassing at these large distances from the sun is not driven the way we expected (super-volatiles rather than water). And again just for me, the most significant discovery from Philae was the existence of a hard surface underneath the soft material at the first touchdown point.
ma

Hi everyone! Thank you so much for doing this AMA. What you all have achieved is just incredible.

With the mission being launched ~10 years ago, and conceived ~25 years ago, what difficulties did you come across using (now) decade old technology? Were there any times you became frustrated because "modern" technology would have made something significantly easier?

The 20 years old technology worked nearly perfectly. The biggest drawback for Philae was the limited computer power and mass memory. What we could install there (800 MHz CPU and some MB memory) seems to be from another world today (ek)

Faster computers always help... and more memory. In the SESAME Experiment, we record time series of vibrations of the soil (CASSE Instrument). This is a kind of seismology. What a seismologist usually wants is: more data. Having just a continuous record over our few days on the comet would make a big difference. But I do not want to complain: we have a lot of data, more than I expected after the first bounce, and I am optimistic that we can make science of it. With the bouncing, it even got more exciting, since we now have data from two points on the comet. mk

Although you all have an intimate understanding of the entire project, do you ever have moments of thinking "are we really controlling a couple of man-made machines as they interact with a comet hundreds of millions of miles away"?

Not in a conspiracy sort of way, but in more of a "the reality of this is insane" way.

It takes a lot of work to keep a missing like Rosetta running. So on a daily basis it is easy to get lost in the details. But it is actually quite incredible that you can talk to a spacecraft 510 million kilometers away through 34 to 70 meter big radio telescopes located all over the world.
The transmission takes place through a microwave signal which is comparable to a flashlight in energy.

We all have those moments the first time we are directly involved with these communications during critical events, but some of us adapt our thinking fairly quickly so that it no longer seems "insane", while others still get that feeling even after doing it many times. For me personally, I no longer think of it as "insane", but neither have I reached the point that I am blasé about it. ma

Thank you :) There have been many surprises during the mission: the strange shape of the comet that made the landing not easier, the hardness of its surface but also the precise landing within some seconds and some dozens of meters of the pre-calculated touchdown scenario (ek)

I think the landing could again be done as it was planned. If the harpoons and ADS would have worked, we would have had a perfect mission on a very good landing site with lot of power for an extensive long term science mission. [mm]

I guess that the rendezvous mission is an important step and will encourage the agencies to think about the next step, a comet nucleus sample return. There are already several proposals on the table
uk

I certainly hope so! On the US side, there are several groups proposing cometary missions to the next round of NASA's Discovery Program (these are small, at least small by NASA standards, missions led by a scientific PI). Those proposals are due early next year and by next summer NASA will select a few, probably 3, of them for more detailed studies, with the final selection in 2016. Whether a cometary mission succeeds is hard to predict, but in the last round a cometary mission was one of the three selected for detailed studies.
There are also at least two teams working longer term on proposals for a sample return mission from the surface of a comet. Those will be submitted to NASA's New Frontiers program (larger, i.e., more expensive missions than the Discovery program). However, the deadline for those proposals has not been announced and it is likely to be in 2016.

OSIRIS has taken more pictures from the orbiter to search for the lander but those images are still on the spacecraft, waiting for their turn to be put into the downlink queue. There have been several suggested identifications of the final landing place in OSIRIS images, but none of these are good enough to be sure, hence the additional images. Tying the images with the information from the CONSERT experiment (talking to Philae through the nucleus can tell them where Philae is by looking at the variations in what is between the orbiter and Philae.
ma

I was already involved in the ESA Giotto mission to comet Halley being in charge of the Halley Multicolour Camera. Right after this mission we started to work on the Rosetta mission and here again I was responsible (PI) of the scientific camera system OSIRIS. Most of my research has been connected to cometary physics.

I think one of the key missions is a comet nucleus sample return. Bringing back a sample of the most pristine material we can imaging will provide a major step in the understanding of the physical and chemical conditions of the early solar system (nebula) out of which our planetary system formed. Investigations in laboratories on earth provide much more capabilities than even the most sophisticated instruments on spacecraft. See the example of Stardust mission.

Honestest answer please! I totally love and support the Rosetta/Philae's cartoon video series since the moment I first saw the first episode. Combination of unreality/fairytale and well-detailed reality is super! And seems the series succeeded well. But I know that some people don't like it, seemingly because not representing the reality enough, or maybe too childish for such a strong science opportunity. How many people in the mission team don't like it? And if you don't like it, why??

We produced several Rosetta movies for different target groups. I don't know (honest answer!) how many people in the mission team like it. For me and my kids it was nice even if not representing the reality in its entire complexity (ek)

You measure the doppler shift (frequency shift) of the X-band radio signal to find the acceleration of the spacecraft caused by the comet. Rosetta is equipped with an ultra stable oscillator which makes this possible.
This directly gives the mass of the comet.

In our planned scenario our mission was expected to be finished when reaching about 2 AU due to a possible overheating of the internal compartment. Now the mission profile changed completely and we expect to restart at 2 AU or less due to the limitation on power. We could not use radioactive sources as this was not possible in Europe. Therefore Rosetta is designed as "green spacecraft". [mm]

To any one in the team! Hi! First of all its great knowing that there are people that among the hardships that humanity is going through these times continue to work on expanding the boundries of knowledge in the day by day basis and continue to inspire others like me to do so as well. My question is, will you make the data collected in the mission open the others to study as well in the general community? I believe that crowd sourcing the analysis of the data and making it accessible to every one who's interested in it (like me) to partake in the understandings of what is being discovered and even help you guys! What do you think?

All data will be archived and are then public. They will be archived in an understandable well calibrated format. This will take some time (1/2 to 1 year) and is additional work for the instrument teams.

Every time I hear of the probability of Philae's next wake up, I'm a bit surprised for I have not heard the mission team members's word which sounds like "Philae might wake up again but instruments/equipments were not designed to survive such a long time in the cold, so Philae cannot work." Does that mean that the instruments/equipments on Philae were designed to survive such a long time in the cold??

When you design space mission you always test the equipment in a certain temperature range (called the qualification range). You then try to ensure that the spacecraft never leaves this range. Philae will get colder than the qualification range which means that we are in terra incognitae. This means that the engineers will not guarantee that the lander will work.

It has on the other hand been seen before that hardware works also after a deep freeze. The Soho spacecraft for example survived a multi year freeze when contact was lost. It has now been working flawlessly for years afterwards.

I'm not an engineer and should not speculate... but we've been in space for ten years, and part of the trajectory brought us much farther out than we are now. This could mean there is a chance to survive a few months more. mk

the travel time of a radio signal is currently close to half an hour. Some additional delays may add since we did not communicate with Philae directly, but relayed through the Deep Space Network on Earth, and through the Rosetta Orbiter. mk

First of all, congratulations. This is a magnificent achievement. Your team managed to send a spacecraft on a 10-year mission, and landed on a moving target some 300 million miles away. Can you, briefly, explain the kind of mathematics and galactic navigational skills required to calculate the necessary trajectory that allowed you to achieve this, in layman's terms?

Thank you! May be you are surprised but even the complex trajectory of Rosetta only follows the gravitational law discovered by Newton centuries ago. But because it is a time dependent N-body problem (gravitation by Sun, several planets and even by the comet) we can be happy to have powerful computers today to get the high accuracy in calculating trajectories needed for such a mission as Rosetta (ek)

This refers to the fact that we landed at the foreseen landing spot, bounced off, hit the surface again for a second time and shortly after reached a final landing position which is not yet known. (ip)

The mission is a tremendous success but this will only be complete when Rosetta operates through the perihelion of comet C-G at the end of next year. We want to observe the increase in activity to more than an order of magnitude beyond what it is now
uk

Thank you! I think Rosetta is a huge success! We already have a lot of very interesting data from all 21 instruments. Rosetta is the first mission that orbits a comet, that lands on it and follows it on its way to the Sun. I had wished that anchoring of Philae would have worked but nothing is perfect, particularly at 500 Mill. km away from home (ek)

For su, ip and mk (or to whom it may concern): from what we know - e.g. from MUPUS' hammer breaking - can we say whether the harpoon anchors would have penetrated the ground and kept Philae there if they had worked?

I wanted to ask a simple thing. It can seem weird, but here you go: are we sure that we know all the elements in Mendeleiev's table? I mean, if your robot on a comet discovered an atom with 83746327 electrons around its core, would that be surprising?

We know quite a number of atoms, and we have theories about which configurations of neutrons and protons would be stable. These theories are still subject to testing, of course, but there is currently no reason to assume that we're missing stable elements. mk

But ok: the heaviest natural element is Uranium (Z=92). All heavier atoms are produced artificially and all of them are radioactive.
"New" atoms could be found (generated).. but the "real heavy ones" all have very short half life... (su)

Since I am not on the lander team I only have second hand information. Apparently the Philae is significantly tilted with respect to the horizontal, but I do not have any quantitative information. When someone closer to the lander operations is on, they can provide better information (our knowledge and understanding is evolving quite rapidly).
ma

One is the picture of Philae above the surface of C-G just before the first landing.
More physics oriented I find the large "wall" of the small lobe at the neck awesome particularly I did not expect the surface to look like this.

What kind of emotions did you perceive during the last minutes before the lander's touchdown? I was watching live stream with some of you and it looked like a total anxiety and laughter, interchangeably. How did your attitude evolved during the project's life?

I'm really curious, because despite I've just started to pursue my scientific career, I've found it's quite hard not to get emotional about even basic projects. (quite different field though, I'm an MD)

Those whose prime goal was to land surely experienced their happiest moments when the lander was brought down successfully. The instrument teams waiting for operations to start experienced further up and downs emotionally, especially towards the end when it was unclear how long the battery would still be alive. (ip)

Very optimistic, that Philae wakes up again.
How much science we will be able to do, will depend on the time we need to re-charge the batteries.
I hope the huge media interest in Rosetta and Philae will also make politicians aware of the attractiveness of science! (su)

For sh: is there a fixed publication date by now for the first post-arrival papers from the orbiter instrument teams? Have those papers been submitted already, and if so, covering data til which time? And ... will the world finally get to see some close-up OSIRIS images (i.e. from the low orbital phase) at the time the papers appear?

There is no fixed publication date, but the hope is that the first round of papers from the orbiter teams, or at least from many of the orbiter teams, will be in early to mid-December. Quite a few papers have been submitted and sent out to independent, scientific referees. The teams are now revising the papers to address the questions raised by the referees. These papers will include papers from the OSIRIS team with some fairly close-up pictures. ma

Where do you see the knowledge of asteroids and comets going in the next 10-20 years? When do you think humans will be able to land on asteroids, and when do you think it will be economically feasible to commercially mine such objects?

Predicting the evolution of knowledge is beyond my skills... economically feasible: I personally do not belive in this. It is simply to expensive to bring stuff out there. returing makes it even more difficult. One example: to mine the Moon for an amount of He3 sufficient for the current power consumption of the US would require a heavy industry at a scale you do not even find in coal mining on earth. The same electrical power could be generated by simply covering all our roofs with solar panels. mk

I also have a question for imaging systems team. We saw some comparisons online between the ROLIS and OSIRIS images, before and after first touchdown, where 4 tracks seem visible on the ground instead of 3. Is there the possibility that one of these was caused by a small rebound on one foot during the first touchdown? Or was it caused by a secondary factor not related with Philae's feet?

It turns out that only one of the spots on the surface was related to the actual landing site. People was a bit quick to interpret the three spots as the landing leg foot print. It turns out that the spots are to far away from each others to be the lander legs. One spot is the touchdown site. Another spot is likely a shadow from the dust plume kicked up by the landing.

Hello! I have been following Rosetta and Philae on Twitter and it was an exciting moment when Philae finally landed!
I have a question that I have been burning to know the answer to. I've noticed that more than once, it was mentioned that the comet surface was soft and "fluffy" so I was wondering if you guys knew the comet surface was like that, how did you ensure that Philae would be able to deploy its harpoons and bind itself to the comet if there was no indication that a hard surface exists few inches (or did you know?) below the surface?

We had expectations of the physical properties from earlier comet flybys and from modeling the activity of comets. The density of comets is low (around 500 kg/m3 or lower) therefore the material is very porous and therefore cannot be really strong. In principle we did not really know what the surface is like (and we still do not know all aspects). From remote sensing you have to make assumptions, therefore is was so important to touch the surface.
Philae was prepared for all kind of surfaces: ice hard with the anchoring drills, loose with the harpoons, and very fluffy using the cold gas to press the lander down.

We have some hope. After some months there should be enough solar energy available to reactivate Philae (when approaching the Sun). The open question is if the lander electronics will survive the low temperatures on the comet (ek)

There are several missions being proposed but unfortunately there are currently no selected mission. I sure hope that the success of Rosetta may change this.

What I would like to see as a result of Philae/Rosetta?... There are of course many questions to be answered but If we understand the way cometary activity works at the end of the mission I will be very happy.
Currently the mission is creating more questions than answers. But this is the way a successful mission always work.

In the US several mission proposals are being studied to bring back material from a comet in order to investigate it in the laboratory. These studies will go ahead independent of what Philae delivers but may be influenced by the Rosetta results.

Clear information about the physical and chemical (organic material?) properties of the surface
uk

Well, it depends on what you mean by planned! We scientists (collectively) have envisioned a variety of future missions to comets (as mentioned in a previous post higher up the page). Some would go to the surface, some would orbit, some might fly past. We have developed plans for how to do the missions, what they would cost, what equipment would be needed, what kind of specialists would be needed, and so on.
On the other hand, neither NASA nor ESA nor JAXA nor IKI nor ISRO has planned to spend money specifically on a cometary mission. The planning process for funding varies dramatically from one space agency to another, but there are certainly plenty of scientists pushing in one way or another, depending on the space agency with which they deal, to get the funding committed for a cometary mission. When that happens, the planning becomes much more intense and much more detailed. ma

Now on to the other question - what would I like to learn from Philae. Given the way Philae behaved, I am very anxious to see the synthesis of all the data, both engineering data and scientific data, that relate to the strength of the cometary material. It seems that at the first touchdown point the lander went into soft material and then suddenly "bottomed out" by hitting a relatively hard surface, from which it bounced. The details of those data will be important in evaluating the details of the materials. We hope to get more images from OSIRIS of that first touchdown spot and analysis of the "crater" that Philae made, and how it evolves over time, will be valuable for understanding how comets work. From the instruments on Philae, I am particularly interested in learning what molecules were identified by the COSAC instrument - even if they were only ambient cometary gases rather than samples brought up from below the surface, the differences between these gases and those seen by the ROSINA mass spectrometer on the orbiter will tell us about the relationship between what is in the nucleus and what we see further out in the coma.
ma

CIVA has taken one successful panoramic image. ROLIS took several on-comet pictures after landing which are currently being investigated. There is an on-board time stamp which can be translated into UTC. (ip)

To design a lander for a cometary mission was a big challenge. The surface properties of a comet were widely unknown. After the postponement of the mission in 2003 we had to find another target (comet Wirtanen was the old one). This was not simple. The selected 67P has more mass and gravitation than Wirtanen what led to some last minute changes in design of the lander (ek)

I did not expect such a diverse surface of the nucleus. The different morphologies are amazing nothing much as a subliming dirt ball. Some of the images you could think where taken on earth. Cliffs, boulders, and dust covered planes. It will take some time to understand how activity (the only eroding force, maybe additional thermal stress or shock) has formed this landscape.

Some of us were looking at the first data which indicated that the lander was in space again. As this was not really a reason to celebrate we waited on further data to learn about the status of the lander. We had a late night celebration upon completion of the first science sequence when the battery depleted Friday night. (ip)

A master or diploma in an appropriate field of science or engineering will do for many positions. Positions to earn a PhD ae often part of the projects. Having a PhD already might also help. The more genius your are, the better - just kidding. We are all normal people. mk